The invention relates to the prefabrication of the throats which connect the hearth of a chimney to the smoke conduit.
The known solutions have various inconveniences.
Certain throats, manufactured by means of plates of cement assembled by tenons and mortices on the site of construction of the chimney, comprise at their upper part a metallic closure element and, under these conditions, the problems of airtightness in regard to the smoke are difficult. Other models are composed of metal plates which are welded or screwed together and their assembly must be carried out in a factory, which clearly complicates the problems of transportation.
In a general manner, the known prefabricated throats are manufactured by assembly of elements which are in relatively large number, in view of the diversity of sizes, and have various practical inconveniences.
The invention seeks to reduce considerably the number of the elements which it is necessary to have in stock, to simplify the assembly with a view to permitting it to be carried out at the construction site in a short time, and to simplify transportation by providing nestable elements, the entirety of these results being obtained without complicating manufacture in the factory and whilst ensuring for the assembled product entirely satisfactory technical qualities.
The throat according to the invention is characterised in that it is obtained by assembly, by simple interengagement, of two identical elements of a first type with two identical elements of a second type, in order to constitute a principal body in the form of a truncated regular pyramid with rectangular base, the elements of the first type having C-sections in planes parallel to the bases and each forming a terminal face and two angle returns of the throat, whilst the elements of the second type join to each other the said angle returns in order to form the front and rear faces of the throat, the said elements being of moulded cast iron and the element of the second type having the form of a trapezium the oblique sides of which are more or less inclined on the base, as a function of the size of the chimney, in such a manner that the horizontal branches of the said C-sections have a length not exceeding a predetermined limit compatible with moulding of the cast iron, without coring.
According to another feature of the invention, the couplings between the branches of the said C-sections are rounded and the joints are arranged to present a smooth surface at the interior of the said principal body.
Other features, as well as the advantages of the invention, will appear clearly in the light of the following description.